A soy allergy causes your immune system to overreact to soy proteins. Symptoms include stomach problems, cough, and itching. A severe soy allergy may cause anaphylaxis. An allergist can diagnose a soy allergy through tests. Treatment includes medications and avoiding products that contain soy.
A soy allergy is a type of food allergy. Your immune system overreacts to soy you’ve ingested (eaten or drunk). For many people, ingesting soy is harmless. However, if you have a soy allergy, your immune system views the protein in soy as a harmful “invader,” like a bacterium or virus.
A soy allergy can be deadly. If you have severe allergic reaction symptoms, such as trouble breathing or swelling in your throat, call 911 or go to your nearest emergency room (ER) immediately.
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A soy allergy can affect anyone of any age. However, infants and young children are more likely to have a soy allergy. You’re also more likely to have a soy allergy if you have other food allergies.
Many infants outgrow a soy allergy as they get older.
Yes. A soy allergy can appear at any age. Certain foods or drinks you previously ingested without any problems can trigger an allergic reaction.
Infants and young children are the most likely to have a soy allergy. Approximately 0.4% of infants in the U.S. are allergic to soy.
A soy allergy causes an allergic reaction in your body. An allergic reaction is your body’s response to an allergen. If you have a soy allergy, your body may have two different types of reactions:
If you have a soy allergy, your body responds by creating immunoglobulin E (IgE) after your first exposure to soy. IgE is an antibody that your immune system makes. Your body makes many different types of IgE, which target specific kinds of allergens.
IgE reactions happen quickly after ingesting soy. Reactions may include anaphylaxis, which is a severe allergic reaction that may cause death.
Non-IgE reactions may involve your immune system, but not your IgE antibodies. Your reaction to soy is slower than an IgE-mediated reaction. It may take up to 48 hours to develop.
Most non-IgE food allergies, including soy, aren’t life-threatening. However, soy is one of the most common triggers for a non-IgE reaction in infants.
Soy allergy symptoms include:
Yes, a soy allergy can cause stomach issues.
You may have stomach cramps, indigestion, diarrhea, nausea and vomiting if you have soy intolerance, which is different than a soy allergy.
Eating a lot of soy may cause inflammation. However, there’s not enough research to conclusively say that soy causes inflammation.
Proteins in soy cause your immune system to overreact.
No, a soy allergy isn’t contagious. You can’t spread a soy allergy to another person.
An allergist is a healthcare provider who specializes in allergies. They can help you diagnose your soy allergy through tests.
Before conducting soy allergy tests, they may ask you questions, including:
Your allergist may use different allergy tests to help diagnose your soy allergy based on your symptoms. These tests may include:
During a blood test, your allergist will use a thin needle (21 gauge, slightly smaller than the size of a standard earring) to withdraw a small amount of blood from a vein in your arm. The blood sample goes to a laboratory. The lab adds soy proteins to your blood sample and measures the levels of IgE antibodies in it.
It may take a week or longer to get the results from a blood test sent to a lab.
This test exposes your body to small amounts of soy proteins.
Your allergist will first clean a test area of your skin with iodine or alcohol. The test area is usually on your forearm or upper back.
Your allergist will use a thin needle (lancet) to prick your skin with a small amount of liquid containing soy proteins. The lancet won’t go deep into your skin. You’ll only feel a tiny pinch, and you won’t bleed.
Some allergists may use a different method for skin testing. They place a droplet of liquid soy proteins on your skin. They then use a lancet to scratch your skin lightly. The droplets will enter your skin through the scratch. You’ll only feel slight discomfort, and you won’t bleed.
After skin testing, you’ll wait 15 minutes. The allergist will then measure any discolored spots on your skin from the soy test or the controls for the test with a ruler.
A skin prick test takes less than an hour.
To definitively diagnose a food allergy, your allergist may recommend a food challenge. This may be necessary if your family history of food allergies and testing don’t match.
During an oral challenge, you’ll eat a small amount of soy. Your allergist will then observe you to see if a reaction develops. You may gradually eat more soy to see how your body responds.
A graded oral challenge may take up to four hours.
If you have a soy allergy, avoiding soy is the only way to prevent a reaction. By law, manufacturers must include soy on the ingredients label of packaged foods sold in the U.S.
If you have a soy allergy, you must consider other possible exposures, including:
Many different foods and drinks contain soy. These include:
It’s also a good idea to be aware of foods that contain natural and artificial flavoring, vegetable broth, vegetable gum and vegetable starch. These foods often contain soy protein.
Items that include hydrolyzed plant protein, hydrolyzed vegetable protein, protein extender and protein filler may include soy protein.
Soy may also be present in foods and drinks such as vodka and nut butters.
Studies show that most people with a soy allergy can safely eat foods that contain soy lecithin and soybean oil. Soybean oil shouldn’t be cold-pressed, expeller-pressed or extruded.
If you have a soy allergy, your healthcare provider should prescribe you an epinephrine auto-injector (EpiPen®). Epinephrine quickly reverses the symptoms of anaphylaxis. Your provider will explain when and how to use this device. You should keep your epinephrine injector with you at all times.
People who have a soy intolerance or a non-IgE-mediated soy allergy don’t need a prescription for epinephrine.
Epinephrine injection side effects may include:
These symptoms are typically mild if they occur, and they go away quickly.
An epinephrine injection starts to work immediately after you’ve injected yourself.
The best way to prevent an allergic reaction to soy is to strictly avoid soy ingredients in foods, drinks and other non-food products.
Check the ingredient labels on all packaged foods. If you’re unsure if a product contains soy, avoid it until you can confirm with the manufacturer.
Living with a soy allergy can be challenging. Symptoms can range from mild to severe, and there’s no way to predict how your body will react. However, with caution, you can leave a fulfilling life. Your healthcare provider can recommend resources, support groups and dietitians to help you with your day-to-day meals.
Infants and young children are more likely to have soy allergies than adults. Most children outgrow a soy allergy by age 10.
See your healthcare provider if you regularly have soy allergy symptoms or if you notice that your symptoms develop after eating soy.
Go to the ER or call 911 if you start showing symptoms of anaphylaxis.
A soy allergy is when your immune system overreacts to soy protein.
A soy intolerance is when your digestive system has a hard time breaking down (digesting) soy. When you ingest soy, you may have symptoms such as gas, diarrhea and abdominal pain.
A note from Cleveland Clinic
A soy allergy is a type of food allergy that occurs when your immune system mistakenly triggers a defensive response to soy. This response — or allergic reaction — can cause various symptoms, including vomiting, stomach cramps, indigestion, diarrhea and, in severe cases, anaphylaxis.
You may feel frustrated not knowing what’s causing your symptoms, but your healthcare provider can help. They can conduct tests to confirm a soy allergy and prescribe medications. They can also refer you to a dietitian who can help you learn what’s best for you to eat and drink.
Last reviewed by a Cleveland Clinic medical professional on 09/15/2022.
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